Projection Systems for Touch Input Devices
In infrared touch input devices that detect and locate a touch object from the blocking of light paths propagating along the X,Y axes, an ambiguity arises when two touch objects are present. This ambiguity can be resolved by the provision of additional light paths angled to the X,Y axes. The present invention provides projection systems that include a light splitting element for splitting collimated sheet of light into two or more sets of beam paths, thereby providing the additional light paths for resolving the double touch ambiguity. In preferred embodiments the light splitting element is in the form of a prism film.
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The present invention relates to projection systems and in particular to the use of such projection systems in touch input devices. The invention has been developed primarily to improve the multi-touch capability of light-based touch input devices and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.
BACKGROUND OF THE INVENTIONAny discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Input devices based on touch sensing (touch screens) have long been used in electronic devices such as computers, personal digital assistants (PDAs), handheld games and point of sale kiosks, and are now appearing in other portable consumer electronics devices such as mobile phones. Generally, touch-enabled devices allow a user to interact with the device by touching one or more graphical elements, such as icons or keys of a virtual keyboard, presented on a display.
Several touch-sensing technologies are known, including resistive, surface capacitive, projected capacitive, surface acoustic wave, optical and infrared, all of which have advantages and disadvantages in areas such as cost, reliability, ease of viewing in bright light, ability to sense different types of touch object, e.g. finger, gloved finger, stylus, and single or multi-touch capability.
The various touch-sensing technologies known differ widely in their multi-touch capability, i.e. their performance when faced with two or more simultaneous touch events. Some early touch-sensing technologies such as resistive and surface capacitive are completely unsuited to detecting multiple touch events, reporting two simultaneous touch events as a ‘phantom touch’ halfway between the two actual points. Certain other touch-sensing technologies have good multi-touch capability but are disadvantageous in other respects. For example projected capacitive touch screens, discussed in US Patent Application Publication No 2006/0097991 A1, only sense certain touch objects (e.g. gloved fingers and non-conductive styluses are unsuitable) and use high refractive index transparent conductive films that are well known to reduce display viewability, particularly in bright sunlight. In another example video camera-based systems, discussed in US Patent Application Publication Nos 2006/0284874 A1 and 2008/0029691 A1, are extremely bulky and unsuitable for hand-held devices. Another touch technology with good multi-touch capability is ‘in-cell’ touch, where an array of sensors are integrated with the display pixels of a display (such as an LCD or OLED display). These sensors are usually photo-detectors (disclosed in U.S. Pat. No. 7,166,966 and US Patent Application Publication No 2006/0033016 A1 for example), but variations involving micro-switches (US 2006/0001651 A1) and variable capacitors (US 2008/0055267 A1), among others, are also known. In-cell approaches cannot be retro-fitted and generally add complexity to the manufacture and control of the displays in which the sensors are integrated. Furthermore those that rely on ambient light shadowing cannot function in low light conditions.
In yet another approach to touch sensing with several possible configurations, a touch event is detected by the shadowing of two paths in a sheet of light (usually in the infrared region) established in front of a display. In one such configuration, illustrated in
In another configuration, illustrated in
In a variant touch input device 17 that greatly reduces the optoelectronic component count, illustrated in
In yet another variant touch input device 30 shown in
A common feature of the touch input devices shown in
In all of the ‘optical’ and ‘infrared’ touch input devices shown in
However even if the correct pair can be identified, say because one touch-down occurred before the other, further complications can arise if the detection system has to track moving touch objects. For example if two moving touch objects (
For ‘optical’ touch input devices, various modifications are known that improve their multi-touch capability. Referring to
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. It is an object of the invention in its preferred form to provide projection systems for infrared touch input devices with improved multi-touch capability.
SUMMARY OF THE INVENTIONAccording to a first aspect the present invention provides a projection system for a touch input device, said projection system comprising:
-
- a first light emitter adapted to emit substantially planar substantially collimated light propagating in a first direction; and
- an optical splitting element adapted to split at least a portion of said substantially planar substantially collimated light into a second direction, different from said first direction.
It will be appreciated that the projection system of the invention comprises apparatus for producing an input signal for a touch input device, wherein the input signal comprises substantially planar substantially collimated light propagating in the first and second directions. Further, it will be appreciated that the touch input device comprises an input area, and that the optical splitting element is positioned between the first light emitter and the input area. It will be understood that light which is ‘split’ is light which is split off from the incident light and redirected or diverted to a different direction.
Preferably the substantially planar substantially collimated light propagating in the first and second directions propagate parallel to the plane of the input area of said touch input device.
It will be appreciated that the optical splitting element is adapted to split at least a portion of the substantially planar substantially collimated light propagating in the first direction into a second direction, different from said first direction. In one embodiment, where the substantially planar substantially collimated light propagating in the first direction is a relatively ‘thick’ sheet of light (say, 10 to 100 microns thick), the portion split into the second direction is an upper (or a lower) portion of the substantially planar substantially collimated light produced by the first light emitter, and the lower (or upper) portion of the substantially planar substantially collimated light continues to propagate, or is allowed to continue to propagate, in the first direction and to traverse the input area of the input device. It will be appreciated that this is effectively a layered structure of a pair of propagating sheets of light. In other embodiments, a ‘sandwich’ structure can be provided, wherein an upper portion is split into the second direction, a middle portion is allowed to propagate in the first direction, and the lower portion is split into yet another direction, or combinations thereof.
In an alternative embodiment, where the substantially planar substantially collimated light propagating in the first direction is a relatively ‘thin’ sheet of light (say, 1 to 5 microns thick), the portion of the substantially planar substantially collimated light split into a second direction is parallel with the light propagating in the first direction. Preferably, in this embodiment, a plurality of spaced portions of light propagating in the first direction are split off by the optical splitting element and redirected into the second direction, thereby to produce a parallel array of light beams propagating in the second direction. In this embodiment the interstitial light not redirected into the second direction is allowed to continue to propagate in the first direction and traverse the input area of the input device. In other words, the optical splitting element splits a plurality of portions of the substantially planar substantially collimated light to produce a plurality of substantially parallel beams of light propagating in said second direction.
Preferably the optical splitting element comprises a prism film or a phase mask such that said substantially planar substantially collimated light propagating in said first and second directions each comprises a plurality of substantially parallel collimated beams of light.
Preferably the optical splitting element is formed on or is integral with an output face of an optical element comprising the first light emitter such that said substantially planar substantially collimated light propagating in said first and second directions each comprises a plurality of substantially parallel collimated beams of light. Preferably each said collimated beam of light is about 0.05 to 5 mm in width. However, it will be appreciated that the widths of the individual beams of light in the first direction may not be the same as the width of those propagating in the second direction.
In one embodiment, the first direction is preferably substantially perpendicular to the output face of the optical splitting element. In this embodiment the first and the second directions are oriented at about 30 to 60 degrees to each other, for example about 45 degrees.
In the embodiment as discussed above, the optical splitting element is adapted to permit a portion of the light propagating in the first direction to continue to propagate in the first direction and traverse the input area of the input device, and a portion of the light is split off into the second direction, which for example is about 45 degrees to the first direction. However, in an alternative embodiment the optical splitting element is adapted to also split a further portion of the substantially planar substantially collimated light propagating in the first direction into a third direction, different from said first and said second directions. In this ‘Y’ embodiment, the leg of the ‘Y’ can be thought of as the first direction, and the arms of the ‘Y’ are the second and third directions, which are preferably about 90 degrees to each other. In yet further embodiments, the ‘Y’ embodiment also includes a portion of light propagating in the first direction. In other words, the optical splitting element is adapted to permit light to propagate in the first direction, as well as splitting light into the second and third directions, and all three ‘sheets’ of light traverse the input area of the input device.
Preferably the input area of the input device is rectangular, with first and fourth mutually opposing sides, and second and third mutually opposing sides. The first light emitter is positioned along the first side of the rectangular input area, and mutually opposed first and second reflectors are positioned along the second and third sides respectively. Positioned along the fourth side are suitable light detectors. It will be appreciated that the light propagating in the first direction propagates across the rectangular input area of the input device, and is received in a first set of detectors positioned along the fourth side. Light propagating in the second direction is reflected off the relevant reflector and then received in a second set of detectors positioned along the fourth side. In the case of the “Y” embodiment above, light propagating in the third direction is reflected off the other reflector and is received in a third set of detectors positioned along the fourth side.
In related embodiments, a second light emitter is provided which is adapted to emit substantially planar substantially collimated light propagating in a fourth direction. The second light emitter is positioned about the periphery of the rectangular input area such that the fourth direction is at substantially 90 degrees to the first direction. Preferably a further optical splitting element is provided adjacent the second light emitter, and is adapted to split at least a portion of said substantially planar substantially collimated light propagating in said fourth direction into a fifth direction, different from said fourth direction.
Preferably the fourth and fifth directions are at about 45 degrees to each other.
Preferably the substantially planar substantially collimated light propagating in said fourth and fifth directions propagates in a direction which is co-planar with or parallel to the plane of the input area of the input device.
It will be appreciated that the further optical splitting element is positioned between the second light emitter and the input area of the input device.
In preferred embodiments the first and second light emitters each comprise a transmissive body comprising a transmissive element adapted to receive, confine and transmit an optical signal in the form of light in substantially planar form, and a collimation and redirection element adapted to substantially collimate and redirect an optical signal, wherein the elements are arranged to receive an optical signal from an optical source and transmit, collimate and redirect the optical signal to produce a substantially collimated signal in a substantially planar form propagating in the first and fourth directions, respectively. In an alternative but related embodiment, the collimation and redirection element comprises a.) a collimation element adapted to substantially collimate an optical signal, and b.) a redirection element adapted to redirect an optical signal, wherein the elements a.) and b.) are arranged to receive an optical signal from an optical source and transmit, collimate and redirect the optical signal to produce a substantially collimated signal in a substantially planar form.
Preferably the first and second light emitters comprise a transmissive body comprising a transmissive element adapted to receive, confine and transmit an optical signal in planar form, and collimation and redirection elements adapted to substantially collimate and redirect optical signals, wherein the elements are arranged to receive first and second optical signals from one or more optical sources and transmit, collimate and redirect said first and second optical signals to produce substantially collimated signals in substantially planar form propagating in said first and fourth directions, respectively.
In preferred embodiments, the first light emitter comprises a plurality of optical sources positioned along a side of the input area of the input device. Alternatively, the first light emitter comprises a plurality of optical waveguides, wherein the distal ends of the optical waveguides are optically coupled to an optical source, and the proximal ends of the optical waveguides are positioned along a side of an input area of said input device.
Preferably the substantially planar substantially collimated light propagating in said first, second, third, fourth, etc. . . . directions are received in corresponding light detecting elements for detecting a touch on or near the input area of the input device.
According to a second aspect the present invention provides a projection system for a touch input device, said projection system comprising:
-
- a transmissive body comprising:
- a collimation element adapted to substantially collimate an optical signal; and
- a redirection element adapted to substantially redirect an optical signal, wherein said collimation and redirection elements are arranged to receive a substantially planar optical signal and collimate and redirect said optical signal to produce a substantially collimated substantially planar signal propagating in a first direction; and
- an optical splitting element adapted to split at least a portion of said substantially collimated substantially planar signal into a second direction, different from said first direction.
Preferably the optical signal is light, and the apparatus comprises an optical source for providing said light. Preferably the light is split into two or more sets of light paths propagating at an angle to each other.
Preferably the transmissive body further comprises a transmissive element adapted to receive, confine and transmit an optical signal in substantially planar form.
According to a third aspect the present invention provides a projection system for a touch input device, said projection system comprising:
-
- a transmissive body comprising a collimation and redirection element adapted to receive a substantially planar optical signal and collimate and redirect said optical signal to produce a substantially collimated substantially planar signal propagating in a first direction; and
- an optical splitting element adapted to split at least a portion of said substantially collimated substantially planar signal into a second direction, different from said first direction.
Preferably the optical signal is light.
Preferably the substantially collimated planar signals propagating in said first and said second directions are directed to corresponding light detecting elements for detecting an input.
According to a fourth aspect the present invention provides a touch input device comprising the apparatus according to the first, second or third aspects.
According to a fifth aspect the present invention provides a method for producing an input signal for an input device, said method comprising the steps of:
-
- providing a substantially planar substantially collimated optical signal propagating in a first direction;
- splitting at least a portion of said substantially planar substantially collimated optical signal into a second direction, different from said first direction; and
- receiving said optical signals propagating in said first and second directions in corresponding light detecting elements for detecting an input.
Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Referring to the drawings,
In the particular embodiment shown in
Turning now to
Referring back to
Details of suitable waveguide materials and patterning techniques can be found for example in US Patent Application Publication Nos US 2007/019033 A1, US 2007/0285406 A1 and US 2007/0258691 A1, and U.S. Pat. No. 7,738,746, the contents of which are incorporated herein by cross reference.
Turning now to
In preferred embodiments, the optical splitting element is in the form of a prism film, i.e. a strip of transparent material with a regular array of miniature prisms. Prism films are produced in large volume by companies such as 3M, typically in a roll-to-roll embossing process, primarily for use as ‘brightness enhancement films’ (BEFs) in displays. Although the particular prism films required for the present application will have a different design from commonly used BEFs, the same manufacturing technology can be used to mass produce suitable prism films once the required master has been fabricated.
where n1, n2 and n3 are the refractive indices of the incidence side medium, the prism film material and the transmission side medium respectively. By way of example, we will consider the situation where the sensing light has wavelength around 850 nm and the prism film is composed of a polycarbonate with refractive index 1.545 at 850 nm To obtain a transmission angle of β=45° for example, and assuming the incidence and transmission side media are air (n1=n3˜1), equation (1) is satisfied for a prism angle α=62.1°.
Turning now to
Turning now to
n3·sin δ=n2·sin(2γ−90) (2)
where n2 and n3 are the refractive indices of the prism film material and the transmission side medium respectively, and γ and δ are in degrees. To obtain a deflection angle of δ=45° for example, and assuming the transmission side medium is air (n3˜1) and the prism film composed of a polycarbonate with n2=1.545 at 850 nm, equation (2) is satisfied for a prism angle γ=58.6°. The critical angle θc for reflection at the angled facet 104 is given by θc=arcsin(n2/n3), so that θc=40.3° if n2=1.545 and n3=1. For an incident beam path 52 propagating perpendicularly to the film base 106, the angle of incidence at the facet 104 is equal to the prism angle γ, which in this example is greater than θc, so that total internal reflection occurs.
Turning now to
Whatever the details of the prism design, it will be appreciated that prism films can be conveniently produced in sheet form by known techniques such as a roll-to-roll embossing process, then cut into linear strips for incorporation into projection systems for touch input devices as shown in
Although the above embodiments show skew beams propagating at 45° to the primary beams, inspection of
n3·sin(δ+γ)=n2·sin γ (3)
where n2 and n3 are the refractive indices of the prism film material and the transmission side medium respectively. Those skilled in the art will understand that a fraction of the incident light will also be internally reflected at the facet 104 and lost to the system, and that this fraction gets larger as the angle of incidence approaches the critical angle. Consequently this prism design is better suited for generating skew beams with relatively small deflection angles δ, as illustrated in
Turning now to
As shown in plan view in
In one embodiment the optical splitting element 120 is in the form of a prism film 128 having a regular array of triangular prisms 130 with angled facets 76 as shown in
In one embodiment the optical splitting element 136 is in the form of a prism film 138 having a regular array of truncated triangular prisms 140 each with two angled facets 76 and a ‘flat’ facet 80 as shown in
In an alternative embodiment the optical splitting element 120 is in the form of a prism film 142 having a regular array of triangular prisms 130 on a pitch 90, separated by flat portions 144 as shown in
n3·sin(γ+δ−90)=n2·sin(3γ−180) (4)
where n2 and n3 are the refractive indices of the prism film material and the transmission side medium respectively, and γ and δ are in degrees. To obtain a deflection angle of δ=45° and assuming the transmission side medium is air (n3˜1) and the prism film composed of a polycarbonate with n2=1.545, equation (4) is satisfied for a prism angle γ=64.1°. Since the angle of incidence at the first angled facet is equal to the prism angle, which is considerably greater than the critical angle θc=40.3° for n2=1.545 and n3=1, total internal reflection will occur. It should be noted that in this embodiment of a prism film the flat portions 144 need to be sufficiently wide to prevent the angled beam paths 122 and 122′ from encountering the adjacent prism.
In all of the above examples where the optical splitting element is in the form of a prism film, the refractive index of the prism film material, n2, appears in the relevant design equation for the angle at which the refracted beams emerge. In general, the refractive index of a material varies with wavelength (via material dispersion) and also with temperature (via the thermo-optic effect), so that the situation of well-defined skew beam directions as shown for example in
By way of example, the magnitude of the material dispersion effect will be evaluated for a polycarbonate prism film 74 as shown in
Turning now to the influence of temperature variations on the deflection angle, we will use a literature value of −0.9×10−4/° C. for the thermo-optic coefficient of polycarbonate (Z. Zhang et al ‘Thermo-optic Coefficients of Polymers for Optical Waveguide Applications’, Polymer vol 47 pp 4893-4896 (2006)). Again considering a prism film 74 with prism angle α=62.1°, we find that for 850 nm light, the deflection angle β will only vary from 45.26° to 44.48° over a temperature range −20 to 100° C., again well within the acceptance angle of typical in-plane lenses.
In alternative embodiments, the optical splitting element may be a diffractive element instead of a refractive element such as a prism film. One type of diffractive element is a phase mask.
In this case, the majority of the incident light will be coupled into the ±1 orders, with diffraction angle θ determined by the wavelength and the grating pitch Λ according to:
These two orders would form the split beams 122, 122′ as shown in
The grating teeth 148 are shown as square in
Several variant phase mask designs will occur to those skilled in the art. For example if the grating depth is chosen such that a significant amount of incident light is coupled into the zero order as well as into the ±1 orders, then a phase mask could serve as the ‘three beam’ optical splitting element 136 in the fourth embodiment projection system shown in
In each of the previously described example embodiments, and as shown schematically in
An optical splitting element in this form, however, would be impractical in situations (e.g. along the sides of a touch input device as shown in
There are also situations where two or more prism films could be stacked and positioned to receive different portions of an incident light sheet, to generate multiple sets of beams or light sheets. In one example, a stack of two prism films 74 shown in
It will be appreciated that the illustrated embodiments provide projection systems for improved infrared touch input devices, with the improvement lying in either enhanced multi-touch capability or reduced bezel width.
Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.
Claims
1. A projection system for a touch input device, said projection system comprising:
- a first light emitter adapted to emit substantially planar substantially collimated light propagating in a first direction; and
- an optical splitting element adapted to split at least a portion of said substantially planar substantially collimated light into a second direction, different from said first direction.
2. A projection system according to claim 1 wherein said first and second directions are parallel to the plane of the input area of said touch input device.
3. A projection system according to claim 1 wherein said optical splitting element splits an upper or lower portion of said substantially planar substantially collimated light into said second direction.
4. A projection system according to claim 1 wherein said optical splitting element splits a plurality of portions of said substantially planar substantially collimated light to produce a plurality of substantially parallel beams of light propagating in said second direction.
5. A projection system according to claim 1 wherein said optical splitting element comprises a prism film or a phase mask.
6. A projection system according to claim 1 wherein said first and second directions are oriented at about 45 degrees to each other.
7. A projection system according to claim 1 wherein said optical splitting element is further adapted to split at least a portion of said substantially planar substantially collimated light into a third direction, different from said first and said second directions.
8. A projection system according to claim 7 wherein said second and said third directions are oriented at about 90 degrees to each other.
9. A projection system according to claim 7 wherein the input area of said input device is rectangular, with first and fourth mutually opposing sides and second and third mutually opposing sides, wherein said first light emitter is positioned along said first side and mutually opposed first and second reflectors are positioned along said second and third sides respectively, the arrangement being such that light propagating in said second direction is reflected off the relevant reflector and received in a first set of detectors positioned along said fourth side, and light propagating in said third direction is reflected off the relevant reflector and received in a second set of detectors positioned along said fourth side.
10. A projection system according to claim 1 wherein a second light emitter is provided which is adapted to emit substantially planar substantially collimated light propagating in a fourth direction.
11. A projection system according to claim 10 wherein said fourth direction is at substantially 90 degrees to said first direction.
12. A projection system according to claim 10 wherein an optical splitting element is provided adjacent the second light emitter, and is adapted to split at least a portion of said substantially planar substantially collimated light propagating in said fourth direction into a fifth direction, different from said fourth direction.
13. A projection system according to claim 12 wherein said fourth and fifth directions are oriented at about 45 degrees to each other.
14. A projection system according to claim 1, wherein said first light emitter comprises a transmissive element adapted to receive, confine and transmit an optical signal in planar form, a collimation element adapted to substantially collimate an optical signal, and a redirection element adapted to redirect an optical signal, wherein said elements are arranged to receive an optical signal from an optical source and transmit, collimate and redirect the optical signal to produce a substantially collimated signal in a substantially planar form.
15. A projection system according to claim 10 wherein said first and second light emitters comprise a transmissive body comprising a transmissive element adapted to receive, confine and transmit an optical signal in planar form, and collimation and redirection elements adapted to substantially collimate and redirect optical signals, wherein the elements are arranged to receive first and second optical signals from one or more optical sources and transmit, collimate and redirect said first and second optical signals to produce substantially collimated signals in substantially planar form propagating in said first and fourth directions, respectively.
16. A projection system for a touch input device, said projection system comprising:
- a transmissive body comprising:
- a collimation element adapted to substantially collimate an optical signal; and
- a redirection element adapted to substantially redirect an optical signal, wherein said collimation and redirection elements are arranged to receive a substantially planar optical signal and collimate and redirect said optical signal to produce a substantially collimated substantially planar signal propagating in a first direction; and
- an optical splitting element adapted to split at least a portion of said substantially collimated substantially planar signal into a second direction, different from said first direction.
17. A projection system for a touch input device, said projection system comprising:
- a transmissive body comprising a collimation and redirection element adapted to receive a substantially planar optical signal and collimate and redirect said optical signal to produce a substantially collimated substantially planar signal propagating in a first direction; and
- an optical splitting element adapted to split at least a portion of said substantially collimated substantially planar signal into a second direction, different from said first direction.
18. A touch input device comprising the projection system according to claim 17.
19. A method for producing an input signal for an input device, said method comprising the steps of:
- providing a substantially planar substantially collimated optical signal propagating in a first direction;
- splitting at least a portion of said substantially planar substantially collimated optical signal into a second direction, different from said first direction; and
- receiving said optical signals propagating in said first and second directions in corresponding light detecting elements for detecting an input.
Type: Application
Filed: Sep 22, 2010
Publication Date: Jan 31, 2013
Patent Grant number: 8810549
Applicant: RPO Pty Limited (Acton, ACT)
Inventors: Warwick Holloway (Kambah), Robert Bruce Charters (Palmerston), Duncan Ian Ross (Acton)
Application Number: 13/497,754
International Classification: G06F 3/042 (20060101);